On Mon, 6 Apr 2015 14:36:16 +0900
Namhyung Kim <namhyung@xxxxxxxxxx> wrote:
> Currently it ignores operator priority and just sets processed args as a
> right operand. But it could result in priority inversion in case that
> the right operand is also a operator arg and its priority is lower.
>
> For example, following print format is from new kmem events.
>
> "page=%p", REC->pfn != -1UL ? (((struct page *)(0xffffea0000000000UL)) + (REC->pfn)) : ((void *)0)
>
> But this was treated as below:
>
> REC->pfn != ((null - 1UL) ? ((struct page *)0xffffea0000000000UL + REC->pfn) : (void *) 0)
>
> In this case, the right arg was '?' operator which has lower priority.
> But it just sets the whole arg so making the output confusing - page was
> always 0 or 1 since that's the result of logical operation.
>
> With this patch, it can handle it properly like following:
>
> ((REC->pfn != (null - 1UL)) ? ((struct page *)0xffffea0000000000UL + REC->pfn) : (void *) 0)
Nice catch. One nit.
>
> Cc: Steven Rostedt <rostedt@xxxxxxxxxxx>
> Signed-off-by: Namhyung Kim <namhyung@xxxxxxxxxx>
> ---
> tools/lib/traceevent/event-parse.c | 17 ++++++++++++++++-
> 1 file changed, 16 insertions(+), 1 deletion(-)
>
> diff --git a/tools/lib/traceevent/event-parse.c b/tools/lib/traceevent/event-parse.c
> index 6d31b6419d37..604bea5c3fb0 100644
> --- a/tools/lib/traceevent/event-parse.c
> +++ b/tools/lib/traceevent/event-parse.c
> @@ -1939,7 +1939,22 @@ process_op(struct event_format *event, struct print_arg *arg, char **tok)
> goto out_warn_free;
>
> type = process_arg_token(event, right, tok, type);
> - arg->op.right = right;
> +
> + if (right->type == PRINT_OP &&
> + get_op_prio(arg->op.op) < get_op_prio(right->op.op)) {
> + struct print_arg tmp;
> +
> + /* swap ops according to the priority */
This isn't really a swap. Better term to use is "rotate".
But other than that,
Acked-by: Steven Rostedt <rostedt@xxxxxxxxxxx>
-- Steve
> + arg->op.right = right->op.left;
> +
> + tmp = *arg;
> + *arg = *right;
> + *right = tmp;
> +
> + arg->op.left = right;
> + } else {
> + arg->op.right = right;
> + }
>
> } else if (strcmp(token, "[") == 0) {
>
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